The storage of data in networks is often based on distributed storage units. There are some architectures of distributed storage systems known, which allow to store data from a plurality of computers on a plurality of storage units:
For example the network attached storage (NAS) supplies file-based data storage services to other devices of a network, whereby a data storage unit or a data storage array, for example a RAID, is accessed on basis of a TCP/IP-based protocol (network file system (NFS), CIFS) over a network, for example Ethernet.
Another example is a storage area network (SAN), which provides block-based storage and leaves file system concerns on the “client” side. The storage area network allows for connecting hard drive subsystems with storage servers. With the help of a cluster file system it is possible to distribute the access operations of clients on the hard drive subsystems in the storage area network to retrieve the blocks of requested files.
A further alternative is the clustered NAS heads (e.g. pNFS, Lustre), whereby the data access is distributed on a plurality of parallel accesses to hard drive subsystems. The access on the data can be block, object or file based.
All these and further distributed network storage systems are usually adapted for all kinds of application, so that on the one hand side short response times for random access and on the other hand side high bandwidths are provided.
The document U.S. Pat. No. 6,721,490 B1 discloses a hierarchical memory scheme capable of improving a hit rate for the segment containing the random access point rather than improving the overall hit rate of the cache, and a data playback scheme capable of automatically detecting positions that are potentially used as playback start indexes by the user and attaching indexes, are disclosed. The hierarchical storage device stores random access point segment information from which a possibility for each segment to contain a point that can potentially be random accessed in future can be estimated, and controls a selection of the selected segments to be stored in the cache storage device according to the random access point segment information. The document US 2006/0080350 A1, now abandoned, discloses a method and a system for allocating storage space in a storage medium for storing data in a single file from at least one application running in an information system. It is proposed that a least one characteristic of a plurality of a plurality of data storage operations is monitored when data is stored on the storage medium for the file by the at least one application. In a next step a storage pattern is identified from the monitored at least one characteristic of the plurality of data storage operations. On basis of this automatically identified storage pattern an amount of storage space to be used for additional data for the file is determined and allocated.
The document EP 1 345 113 A2 represents the closest prior art and discloses a management server, which manages the physical data areas, which storage devices have, as virtual data areas. In order to improve the efficiency of the management server, a read-ahead procedure is implemented, whereby the server adds new entries to a readahead history information in case data is retrieved from the virtual data areas and uses the readahead history information in case for checking whether or not the data that becomes the read-out target the next time has been already read out onto caches by a previous readahead processing.